Since the kidneys filter or remove waste products and excess fluids from the blood, approximately one-third of the blood delivered from the heart flows through the kidneys. This flow of blood also allows the kidneys to play a major role in regulating the blood pressure in a person. When the build-up of plaque (atherosclerosis), as well as other abnormalities that may occur in the renal artery, cause enough narrowing or blockage of the artery such that the supply of blood to the kidney is reduced, the risk of kidney damage becomes very high. If this condition, i.e., renal artery stenosis, is left untreated it can lead to high blood pressure, reduced functioning of the kidneys, and/or even kidney failure.
A standard procedure used in the treatment of endovascular diseases and abnormalities is the placement of medical devices, such as embolic coils, stents, and dilation balloons, among others, at a desired or targeted site within a patient. The delivery of such a medical device has typically been accomplished by a variety of means, including the use of a catheter through which the device travels for deployment to the targeted site. These medical devices usually have a contracted shape that allows them to pass through the lumen of the catheter and an expanded shape for engagement with the body vessel that occurs after being deployed at the targeted site.
A renal stent is an example of such a medical device. The stent acts as a scaffold, by keeping the artery stretched open and maintaining adequate blood flow through the vessel. However, because renal artery stents are exposed to the flow of blood, they may facilitate the formation of clots until the stent becomes covered with tissue from the body. Various medications are usually given to the patient at this time to prevent the occurrence of thrombosis, i.e., the formation of a blood clot.
In order to increase the safety of using stents and other devices in the vasculature of a patient, embolic protection devices have been developed as a means to capture blood clots and other embolic particles that may become dislodged from a stenosis or the treatment thereof. Such devices may be deployed within a vessel at a site distal, e.g., downstream, to the stenosis before the treatment takes place. In a deployed configuration, the embolic protection device is intended to act as a filter that allows blood to pass through, but traps any embolic particles, such as atherosclenotic plaque or a thrombus, attempting to flow therewith.
Multiple issues exist with the design, manufacturing, and use of existing filter devices. Among these issues is the desirability under certain circumstances to deploy the filter device from the proximal side of the stenosed region. Therefore, the profile of the filtering device should be smaller than the opening through the stenosed region. Another issue, among many, resides in the filter portion being susceptible to becoming clogged or occluded during treatment, thereby, reducing the blood flow through the blood vessel. Accordingly, there is a continual desire to provide improved devices and methods for capturing emboli within a blood vessel. A filter device that provides distal protection during a procedure that has the potential to produce emboli without substantially restricting blood flow through the vessel would be beneficial.